Researchers have 3D printed a new biopolymer made from shrimp – the results may change the the way things are made.

Applications of the conductive self-healing (CSH) hydrogel include soft robots, biomimetic prostheses, and health-monitoring systems. The material mimics human skin with its ability to self-heal.

The scientists say, “Considering the superb sensing performance pairing with self-healing property, 3D printability, and stretchability, the developed material offers superior functionalities compared with the previously reported ones.

Some of these superior properties include 100% mechanical recovery in 2 min, ultrastretchability (1500%), and pressure sensitivity. The work was performed by scientists from Chongqing’s Military Medical University and Canada’s University of Manitoba.

After 3D printing the wearable sensor was tested. Image via Journal of Advanced Materials.

After 3D printing the wearable sensor was tested. Image via Journal of Advanced Materials.

3D printing with shrimp

To make the 3D printable CSH hydrogel an organic and conductive polymer was combined with chitosan. Chitosan is produced using the shells of crabs, shrimp and other crustaceans. Applications of chitosan involve harnessing its many properties, such as an antibacterial agent and ability to rapidly clot blood.

NASA has used chitosan to grow plants in space and the U.S. Marine Corp has tested a gauze dressing incorporating the material. Other applications include a coating made from the material that could be applied to cars and would self-heal damage to the paint work.

The researchers say an important feature of their hydrogel is, “injectability which enables to [3D] print a CSH hydrogel for the first time.

Key to this is the “Autonomic repeatable self-repairing capability after damage and shear-thinning behavior [that] enables these hydrogels to be used as 3D printing materials.”

A soft-robotic octopus. Credit to Jennie Hills, London Science Museum.

Soft-robotic devices can often resemble sea creatures, such as this octopus. Credit to Jennie Hills, London Science Museum.

3D printed wearable devices

After formulation the team tested the hydrogel by 3D printing wearable devices.

These tests included a patch that could monitor pulse rate and muscle movement. The “real-time bodily motion monitoring system was designed using smart phones and 3D printed CSH hydrogel.”

Tests involved attaching the device to the chest to monitor respiration, the results showed the electrical changes associated with inhalation and exhalation could be recorded for slow and deep breathing. Also, monitoring of wrist pulses was performed.

In each test, “the results completely conformed to the realistic physiological behaviors.”

The process for making the 3D printed wearable devices is described as follows,

CSH hydrogel was printed on the APS-contained gelatin membrane which is the sacrificial layer. Afterward, the gelatin together with 3D pattern was placed on a thin PDMS membrane from the printed side. Hot water was added to wash the gelatin; and it was found that duration of 2 min was enough to wash the gelatin. Meanwhile, the second solidification occurred, since APS initiator was incubated in gelatin membrane and released in the presence of hot water. Two-sided copper tapes were used to connect the ends of printing for collecting signals.

The Self-healing property of the H2010h1 hydrogel. Image via the Journal of Advanced Materials.

The Self-healing property of the H2010h1 hydrogel. Image via the Journal of Advanced Materials.

The research was led by Malcolm Xing with Mohammad Ali Darabi, Ali Khosrozadeh, Rene Mbeleck, Yuqing Liu, Qiang Chang, Junzi Jiang, Jun Cai, Quan Wang and Gaoxing Luo.

The full article, “Skin-Inspired Multifunctional Autonomic-Intrinsic Conductive Self-Healing Hydrogels with Pressure Sensitivity, Stretchability, and 3D Printability” is available here.

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Featured image shows another self healing method involving shrimp – Michelada con Camarones.

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